This feature automatically adjusts screen brightness according to the ambient level of light around your phone. The bar moves automatically according to the ambient brightness to adjust screen brightness automatically.
How to enable automatic brightness
• 'Automatic brightness' can be enabled in settings.
• 'Automatic brightness' can also be set by tapping 'Auto' in Quick Settings under notifications panel.
• Even when using the automatic brightness function, the brightness adjustment bar can be tapped to adjust screen brightness to the desired level.